Disperse non-polyalphaolefin drag reducing polymers

ABSTRACT

A drag reducing composition comprising at least one non-polyalphaolefin polymer having an average particle size in the range of from about 5 to about 800 micrometers. The non-polyalphaolefin polymer can initially be formed via emulsion polymerization. The initial polymer particles can then be at least partially consolidated and then reduced in size and suspended in a carrier fluid. The resulting drag reducing composition can be added to a hydrocarbon-containing fluid to decrease the pressure drop associated with the turbulent flow of the hydrocarbon-containing fluid through a conduit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/925,214, filed Oct. 26, 2007, which is herein incorporated byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to drag reducing compositionscomprising disperse polymer particles. In another aspect, the presentinvention relates to drag reducing compositions comprising at least onedrag reducing polymer made by emulsion polymerization.

2. Description of the Prior Art

When fluids are transported by a pipeline, a drop in fluid pressuretypically occurs due to friction between the wall of the pipeline andthe fluid. Due to this pressure drop, for a given pipeline, fluid mustbe transported with sufficient pressure to achieve a desired throughput.When higher flow rates are desired through the pipeline, more pressuremust be applied due to the fact that as flow rates are increased thedifference in pressure caused by the pressure drop also increases.However, design limitations on pipelines limit the amount of pressurethat can be employed. The problems associated with pressure drop aremost acute when fluids are transported over long distances. Suchpressure drops can result in inefficiencies that increase equipment andoperation costs.

To alleviate the problems associated with pressure drop, many in theindustry utilize drag reducing additives in the flowing fluid. When theflow of fluid in a pipeline is turbulent, high molecular weightpolymeric drag reducers can be employed to enhance the flow. A dragreducer is a composition capable of substantially reducing friction lossassociated with the turbulent flow of fluid through a pipeline. The roleof these additives is to suppress the growth of turbulent eddies, whichresults in higher flow rate at a constant pumping pressure. Ultra-highmolecular weight polymers are known to function well as drag reducers,particularly in hydrocarbon liquids. In general, drag reduction dependsin part upon the molecular weight of the polymer additive and itsability to dissolve in the hydrocarbon under turbulent flow. It has beenfound that effective drag reduction can be achieved by employing dragreducing polymers having molecular weights in excess of five million.However, despite these advances in the field of drag reducing polymers,a need still exists for improved drag reducers.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, there is provided a processfor preparing a drag reducer. The process of this embodiment comprises:(a) consolidating a plurality of initial particles comprising at leastone polymer prepared via emulsion polymerization to thereby form one ormore consolidated polymer structures; (b) decreasing the size of atleast a portion of the consolidated polymer structures to thereby form aplurality of modified polymer particles; and (c) dispersing at least aportion of the modified polymer particles in a carrier fluid to therebyform the drag reducer.

In another embodiment of the present invention, there is provided a dragreducer comprising a plurality of particles comprising anon-polyalphaolefin polymer. The particles are dispersed in a carrierfluid and have an average particle size in the range of from about 5 toabout 800 micrometers. The polymer has a weight average molecular weightof at least about 1×10⁶ g/mol.

In yet another embodiment of the present invention, there is provided amethod for reducing drag in a pipeline. The method of this embodimentcomprises: (a) introducing a drag reducer into a hydrocarbon-containingfluid to thereby form a treated hydrocarbon-containing fluid; and (b)flowing the treated hydrocarbon-containing fluid through a pipeline. Thedrag reducer comprises a disperse phase comprising a plurality ofparticles comprising a non-polyalphaolefin polymer. The particles havean average particle size in the range of from about 5 to about 800micrometers. The polymer has a weight average molecular weight of atleast about 1×10⁶ g/mol.

DETAILED DESCRIPTION

In accordance with one embodiment of the present invention, a dragreducing composition (i.e., a drag reducer) is provided comprising acarrier fluid and a plurality of particles comprising anon-polyalphaolefin polymer. The non-polyalphaolefin polymer particlesof the present invention can be prepared by first forming polymerparticles via emulsion polymerization, followed by consolidating atleast a portion of these initial particles into one or more consolidatedpolymer structures. Next, the size of the resulting consolidated polymerstructures can be decreased, and the resulting modified polymerparticles can be dispersed in the carrier fluid. The drag reducer of thepresent invention can be employed to at least partially reduce thepressure drop associated with the turbulent flow of ahydrocarbon-containing fluid through a conduit (e.g., a pipeline).

As mentioned above, the first step in producing the non-polyalphaolefinpolymer particles of the present invention can be performed by preparinga non-polyalphaolefin polymer via emulsion polymerization. This step cancomprise the emulsion polymerization of a reaction mixture comprisingone or more monomers, a continuous phase, at least one surfactant, andan initiation system. As used herein, the term “emulsion polymer” shalldenote any polymer prepared via emulsion polymerization.

As discussed in greater detail below, the resulting reaction product ofthe emulsion polymerization can be in the form of a latex compositioncomprising a disperse phase of non-polyalphaolefin particles (a.k.a.,initial particles). The continuous phase of the latex compositiongenerally comprises at least one component selected from the groupconsisting of water, polar organic liquids (e.g., alcohol), and mixturesthereof. When water is the selected constituent of the continuous phase,the reaction mixture can also comprise a buffer. Additionally, asdescribed in more detail below, the continuous phase can optionallycomprise a hydrate inhibitor.

In one embodiment of the present invention, the non-polyalphaolefinpolymer prepared via emulsion polymerization can comprise a plurality ofrepeating units of the residues of one or more of the monomers selectedfrom the group consisting of:

wherein R₁ is H or a C1-C10 alkyl radical, and R₂ is H, a C1-C30 alkylradical, a C5-C30 substituted or unsubstituted cycloalkyl radical, aC6-C20 substituted or unsubstituted aryl radical, an aryl-substitutedC1-C10 alkyl radical, a —(CH2CH2O)_(x)—R_(A) or —(CH2CH(CH3)O)_(x)-R_(A)radical wherein x is in the range of from 1 to 50 and R_(A) is H, aC1-C30 alkyl radical, or a C6-C30 alkylaryl radical;

R₃-arene-R₄   (B)

wherein arene is a phenyl, naphthyl, anthracenyl, or phenanthrenyl, R₃is CH═CH₂ or CH₃—C═CH₂, and R₄ is H, a C1-C30 alkyl radical, a C5-C30substituted or unsubstituted cycloalkyl radical, Cl, SO₃, OR_(B), orCOOR_(C), wherein R_(B) is H, a C1-C30 alkyl radical, a C5-C30substituted or unsubstituted cycloalkyl radical, a C6-C20 substituted orunsubstituted aryl radical, or an aryl-substituted C1-C10 alkyl radical,and wherein R_(C) is H, a C1-C30 alkyl radical, a C5-C30 substituted orunsubstituted cycloalkyl radical, a C6-C20 substituted or unsubstitutedaryl radical, or an aryl-substituted C1-C10 alkyl radical;

wherein R₅ is H, a C1-C30 alkyl radical, or a C6-C20 substituted orunsubstituted aryl radical;

wherein R₆ is H, a C1-C30 alkyl radical, or a C6-C20 substituted orunsubstituted aryl radical;

wherein R₇ is H or a C1-C18 alkyl radical, and R₈ is H, a C1-C18 alkylradical, or Cl;

wherein R₉ and R₁₀ are independently H, a C1-C30 alkyl radical, a C6-C20substituted or unsubstituted aryl radical, a C5-C30 substituted orunsubstituted cycloalkyl radical, or heterocyclic radicals;

wherein R₁₁ and R₁₂ are independently H, a C1-C30 alkyl radical, aC6-C20 substituted or unsubstituted aryl radical, a C5-C30 substitutedor unsubstituted cycloalkyl radical, or heterocyclic radicals;

wherein R₁₃ and R₁₄ are independently H, a C1-C30 alkyl radical, aC6-C20 substituted or unsubstituted aryl radical, a C5-C30 substitutedor unsubstituted cycloalkyl radical, or heterocyclic radicals;

wherein R₁₅ is H, a C1-C30 alkyl radical, a C6-C20 substituted orunsubstituted aryl radical, a C5-C30 substituted or unsubstitutedcycloalkyl radical, or heterocyclic radicals;

wherein R₁₆ is H, a C1-C30 alkyl radical, or a C6-C20 aryl radical;

wherein R₁₇ and R₁₈ are independently H, a C1-C30 alkyl radical, aC6-C20 substituted or unsubstituted aryl radical, a C5-C30 substitutedor unsubstituted cycloalkyl radical, or heterocyclic radicals; and

wherein R₁₉ and R₂₀ are independently H, a C 1-C30 alkyl radical, aC6-C20 substituted or unsubstituted aryl radical, a C5-C30 substitutedor unsubstituted cycloalkyl radical, or heterocyclic radicals.

As mentioned above, the emulsion polymer of the present invention cancomprise a non-polyalphaolefin polymer. Additionally, the emulsionpolymer can comprise repeating units of the residues of C4-C20 alkyl,C6-C20 substituted or unsubstituted aryl, or aryl-substituted C1-C10alkyl ester derivatives of methacrylic acid or acrylic acid. In anotherembodiment, the emulsion polymer can be a copolymer comprising repeatingunits of the residues of 2-ethylhexyl methacrylate and the residues ofat least one other monomer. In yet another embodiment, the emulsionpolymer can be a copolymer comprising repeating units of the residues of2-ethylhexyl methacrylate monomers and butyl acrylate monomers. In stillanother embodiment, the emulsion polymer can be a homopolymer comprisingrepeating units of the residues of 2-ethylhexyl methacrylate.

The surfactant used in the above-mentioned reaction mixture can includeat least one high HLB anionic or nonionic surfactant. The term “HLBnumber” refers to the hydrophile-lipophile balance of a surfactant in anemulsion. The HLB number is determined by the methods described by W. C.Griffin in J. Soc. Cosmet. Chem., 1, 311 (1949) and J. Soc. Cosmet.Chem., 5, 249 (1954), which are incorporated herein by reference. Asused herein, the term “high HLB” shall denote an HLB number of 7 ormore. The HLB number of surfactants for use with forming the reactionmixture can be at least about 8, at least about 10, or at least 12.

Exemplary high HLB anionic surfactants include, but are not limited to,high HLB alkyl sulfates, alkyl ether sulfates, dialkyl sulfosuccinates,alkyl phosphates, alkyl aryl sulfonates, and sarcosinates. Suitableexamples of commercially available high HLB anionic surfactants include,but are not limited to, sodium lauryl sulfate (available as RHODAPON LSBfrom Rhodia Incorporated, Cranbury, N.J.), dioctyl sodium sulfosuccinate(available as AEROSOL OT from Cytec Industries, Inc., West Paterson,N.J.), 2-ethylhexyl polyphosphate sodium salt (available from JarchemIndustries Inc., Newark, N.J.), sodium dodecylbenzene sulfonate(available as NORFOX 40 from Norman, Fox & Co., Vernon, Calif.), andsodium lauroylsarcosinate (available as HAMPOSYL L-30 from HampshireChemical Corp., Lexington, Mass.).

Exemplary high HLB nonionic surfactants include, but are not limited to,high HLB sorbitan esters, PEG fatty acid esters, ethoxylated glycerineesters, ethoxylated fatty amines, ethoxylated sorbitan esters, blockethylene oxide/propylene oxide surfactants, alcohol/fatty acid esters,ethoxylated alcohols, ethoxylated fatty acids, alkoxylated castor oils,glycerine esters, linear alcohol ethoxylates, and alkyl phenolethoxylates. Suitable examples of commercially available high HLBnonionic surfactants include, but are not limited to, nonylphenoxy andoctylphenoxy poly(ethyleneoxy) ethanols (available as the IGEPAL CA andCO series, respectively from Rhodia, Cranbury, N.J.), C8 to C18ethoxylated primary alcohols (such as RHODASURF LA-9 from Rhodia Inc.,Cranbury, N.J.), C11 to C15 secondary-alcohol ethoxylates (available asthe TERGITOL 15-S series, including 15-S-7, 15-S-9, 15-S-12, from DowChemical Company, Midland, Mich.), polyoxyethylene sorbitan fatty acidesters (available as the TWEEN series of surfactants from Uniquema,Wilmington, Del.), polyethylene oxide (25) oleyl ether (available asSIPONIC Y-500-70 from Americal Alcolac Chemical Co., Baltimore, Md.),alkylaryl polyether alcohols (available as the TRITON X series,including X-100, X-165, X-305, and X-405, from Dow Chemical Company,Midland, Mich.).

In one embodiment, the initiation system for use in the above-mentionedreaction mixture can be any suitable system for generating free radicalsnecessary to facilitate emulsion polymerization. Possible initiatorsinclude, but are not limited to, persulfates (e.g., ammonium persulfate,sodium persulfate, potassium persulfate), peroxy persulfates, andperoxides (e.g., tert-butyl hydroperoxide) used alone or in combinationwith one or more reducing components and/or accelerators. Possiblereducing components include, but are not limited to, bisulfites,metabisulfites, ascorbic acid, erythorbic acid, and sodium formaldehydesulfoxylate. Possible accelerators include, but are not limited to, anycomposition containing a transition metal having two oxidation statessuch as, for example, ferrous sulfate and ferrous ammonium sulfate.Alternatively, known thermal and radiation initiation techniques can beemployed to generate the free radicals. In another embodiment, anypolymerization and corresponding initiation or catalytic methods knownby those skilled in the art may be used in the present invention. Forexample, when polymerization is performed by methods such as addition orcondensation polymerization, the polymerization can be initiated orcatalyzed by methods such as cationic, anionic, or coordination methods.

When water is used to form the above-mentioned reaction mixture, thewater can be purified water such as distilled or deionized water.However, the continuous phase of the emulsion can also comprise polarorganic liquids or aqueous solutions of polar organic liquids, such asthose listed below.

As previously noted, the reaction mixture optionally can include abuffer. The buffer can comprise any known buffer that is compatible withthe initiation system such as, for example, carbonate, phosphate, and/orborate buffers.

As previously noted, the reaction mixture optionally can include atleast one hydrate inhibitor. The hydrate inhibitor can be athermodynamic hydrate inhibitor such as, for example, an alcohol and/ora polyol. In one embodiment, the hydrate inhibitor can comprise one ormore polyhydric alcohols and/or one or more ethers of polyhydricalcohols. Suitable polyhydric alcohols include, but are not limited to,monoethylene glycol, diethylene glycol, triethylene glycol,monopropylene glycol, and/or dipropylene glycol. Suitable ethers ofpolyhydric alcohols include, but are not limited to, ethylene glycolmonomethyl ether, diethylene glycol monomethyl ether, propylene glycolmonomethyl ether, and dipropylene glycol monomethyl ether.

In forming the reaction mixture, the monomer, water, the at least onesurfactant, and optionally the hydrate inhibitor, can be combined undera substantially oxygen-free atmosphere that is maintained at less thanabout 1,000 ppmw oxygen or less than about 100 ppmw oxygen. Theoxygen-free atmosphere can be maintained by continuously purging thereaction vessel with an inert gas such as nitrogen and/or argon. Thetemperature of the system can be kept at a level from the freezing pointof the continuous phase up to about 60° C., in the range of from about 0to about 45° C., or in the range of from 0 to 30° C. The system pressurecan be maintained in the range of from about 5 to about 100 psia, in therange of from about 10 to about 25 psia, or about atmospheric pressure.However, higher pressures up to about 300 psia can be necessary topolymerize certain monomers, such as diolefins.

Next, a buffer can be added, if required, followed by addition of theinitiation system, either all at once or over time. The polymerizationreaction is carried out for a sufficient amount of time to achieve atleast about 90 percent conversion by weight of the monomers. Typically,this time period is in the range of from between about 1 to about 10hours, or in the range of from 3 to 5 hours. During polymerization, thereaction mixture can be continuously agitated.

The following table sets forth approximate broad and narrow ranges forthe amounts of the ingredients present in the reaction mixture.

Ingredient Broad Range Narrow Range Monomer (wt. % of  10-60%  30-50%reaction mixture) Water (wt. % of  20-80%  50-70% reaction mixture)Surfactant (wt. % of  0.1-10% 0.25-6%  reaction mixture) Initiationsystem Monomer:Initiator 1 × 10³:1-5 × 10⁶:1 5 × 10³:1-2 × 10⁶:1 (molarratio) Monomer:Reducing Comp. 1 × 10³:1-5 × 10⁶:1 1 × 10⁴:1-2 × 10⁶:1(molar ratio) Accelerator:Initiator 0.001:1-10:1   0.005:1-1:1    (molarratio) Buffer 0 to amount necessary to reach pH of initiation (initiatordependent, typically between about 6.5-10) Optional hydrate inhibitor Ifpresent, the hydrate inhibitor can have a hydrate inhibitor-to-waterweight ratio from about 1:10 to about 10:1, about 1:5 to about 5:1, or2:3 to 3:2.

The emulsion polymerization reaction yields a latex compositioncomprising a disperse phase of solid particles and a liquid continuousphase at room temperature. The latex can be a stable colloidaldispersion comprising a disperse phase of high molecular weight polymerparticles and a continuous phase comprising water. The polymer particlescan make up in the range of from about 10 to about 60 percent by weightof the latex, or in the range of from 40 to 50 percent by weight of thelatex. The continuous phase can comprise water, the high HLB surfactant,the hydrate inhibitor (if present), and buffer as needed. Water can bepresent in the range of from about 20 to about 80 percent by weight ofthe latex, or in the range of from about 40 to about 60 percent byweight of the latex. The high HLB surfactant can make up in the range offrom about 0.1 to about 10 percent by weight of the latex, or in therange of from 0.25 to 6 percent by weight of the latex. As noted in thetable above, the buffer can be present in an amount necessary to reachthe pH required for initiation of the polymerization reaction and isinitiator dependent. Typically, the pH required to initiate a reactionis in the range of from 6.5 to 10.

When a hydrate inhibitor is employed in the reaction mixture, it can bepresent in the resulting latex in an amount that yields a hydrateinhibitor-to-water weight ratio in the range of from about 1:10 to about10:1, in the range of from about 1:5 to about 5:1, or in the range offrom 2:3 to 3:2. Alternatively, all or part of the hydrate inhibitor canbe added to the latex after polymerization to provide the desired amountof hydrate inhibitor in the continuous phase of the latex.

In one embodiment of the present invention, the emulsion polymer of thedisperse phase of the latex can have a weight average molecular weight(“M_(W)”) of at least about 1×10⁶ g/mol, at least about 2×10⁶ g/mol, orat least 5×10⁶ g/mol. The initial emulsion polymer particles can have amean particle size of less than about 1 micrometer (“μm”), in the rangeof from about 10 to about 500 nanometers (“nrn”), or in the range offrom 50 to 250 nm. At least about 95 percent by weight of the initialemulsion polymer particles in the latex can be larger than about 10 nmand smaller than about 500 nm. Further, at least about 95 percent byweight of the particles can be larger than about 25 nm and smaller thanabout 250 nm.

As previously noted, after the emulsion polymer has been prepared, atleast a portion of the initial polymer particles in the latex can beconsolidated in order to form one or more consolidated polymerstructures. As used herein, the term “consolidated polymer structure”shall denote polymer particles or structures having an increased averageparticle size compared to the average particle size of the polymerparticles prior to consolidation. Consolidation of the initial latexparticles can be accomplished by any method known in the art capable ofproducing consolidated polymer structures. In one embodiment of thepresent invention, consolidation can be performed using any techniquesufficient to produce consolidated polymer structures having an averageparticle size at least about 5 times, at least about 10 times, or atleast 100 times the average particle size of the initial particles priorto consolidation.

In one embodiment of the present invention, consolidation of the initialemulsion polymer particles can be accomplished by subjecting the latexto a drying step. Consolidation by drying can be accomplished by anydrying method known in the art capable of removing of at least a portionof the continuous phase of the latex described above. In one embodiment,the drying technique employed can be sufficient to remove at least about70 weight percent, at least about 90 weight percent, or at least 95weight percent of the continuous phase of the latex.

In one embodiment, the drying technique employed to form theabove-mentioned consolidated polymer structures can be spray drying.Spray drying is a method of drying materials having both liquid andsolid phases, including such materials as latexes, colloids, andsuspensions. Any spray drying method known in the art can be employed asthe consolidation technique in the present invention. Additionally, thespray drying technique employed in the present invention can comprise atleast two steps: (1) atomization and (2) gas/droplet mixing.

Any atomization technique known in the industry can be employed in thepresent invention that is capable of atomizing the latex formed viaemulsion polymerization discussed above. In one embodiment, the latexcan be atomized employing an atomizer. The latex droplets formed by theatomizer can have an average diameter in the range of from about 1 toabout 500 μm, in the range of from about 25 to about 350 μm, or in therange of from 50 to 200 μm. The atomizer employed in the presentinvention can be any atomizer known in the art. Examples of suitableatomizers include, but are not limited to, high-pressure nozzles,two-fluid nozzles, and high-speed centrifugal disks.

Once the latex has been atomized, the resulting droplets can then becontacted with a gas stream to at least partially vaporize thecontinuous phase of the latex. The gas stream suitable for use in thepresent invention can be air and/or an inert gas. The temperature of thegas stream can be any temperature sufficient to vaporize at least aportion of the continuous phase of the latex. Additionally, the flow ofthe gas stream can be counter-current or co-current with the flow of theatomized latex. The droplet/gas mixing time can be any length of timesufficient to produce consolidated polymer structures having increasedparticle sizes as discussed above. Additionally, the droplet/gas mixingcan be sufficient to remove at least about 70 weight percent, at leastabout 90 weight percent, or at least 95 weight percent of the continuousphase of the latex.

In one embodiment, a partitioning agent can be added to the latex priorto and/or during spray drying to control the amount of agglomeration ofthe polymer. Any partitioning agent known in the industry for limitingpolymer agglomeration can be employed in the present invention. Examplesof suitable partitioning agents include, but are not limited to,alumina, silica, calcined clay, talc, carbon black, calcium stearate,and/or magnesium stearate. The amount of partitioning agent employed inthe spray drying process can be varied depending on the extent ofagglomeration desired. In one embodiment, the partitioning agent can bepresent in an amount in the range of from about 0.1 to about 40 weightpercent, in the range of from about 1 to about 30 weight percent, or inthe range of from 2 to 25 weight percent based on the combined weight ofthe latex and partitioning agent.

In another embodiment of the present invention, the drying techniqueemployed to form the above-mentioned consolidated polymer structures canbe thin-layer drying. The thin-layer drying technique suitable for usein the present invention can be any method known in the art thatevaporates at least a portion of the continuous phase of the latex,leaving behind a thin layer of film comprising one or more of theabove-mentioned consolidated polymer structures.

In one embodiment, thin-layer drying of the latex can be achieved byplacing the latex into a mold, which can be in the shape of a tray orpan. The latex can then be spread into a thin layer. Any method known inthe art capable of creating the desired thickness can be employed forspreading the latex in the mold. For example, the latex can be spread inthe mold by various mechanical processes to create the desiredthickness. Once spread, the latex can have a thickness of less thanabout 1 inch, less than about 0.75 inches, or less than 0.5 inches. Inone embodiment, the pan or tray employed in the present invention can bea moving conveyor-type surface in order to make the drying processcontinuous.

Evaporation of at least a portion of the continuous phase of the latexcan be achieved by any method known in the art of thin-layer drying. Forexample, evaporation can be promoted by forced convection in which drygas, such as air or nitrogen, is blown over the surface of the latex. Asanother example, evaporation can be achieved by employing a spin coatingtechnique. Spin coating is a process whereby the latex is placed on asubstrate and then spun at a high speed. Centripetal acceleration causesthe latex to spread leaving behind the above-mentioned thin layer offilm. Additionally, the latex can be heated to promote evaporation ofthe continuous phase. This can be done by heating the surface on whichthe thin film is being formed and/or by heating the gas that is beingforced across it. Furthermore, the latex can be subjected to vacuumconditions to promote evaporation of the carrier fluid. Regardless ofwhich method is employed, at least about 70 weight percent, at leastabout 90 weight percent, or at least 95 weight percent of the continuousphase can be evaporated during thin-layer drying.

The thickness of the resulting film can vary depending on which methodor combination of methods is employed. Additionally, film thickness canbe affected by viscosity of the continuous phase and percent solids ofthe latex, among others. In general, however, the thickness of theresulting one or more consolidated polymer structures (i.e., the “thinlayer”) formed via thin-layer drying can be in the range of from about0.001 to about 0.25 inches, in the range of from about 0.005 to about0.2 inches, or in the range of from 0.01 to 0.15 inches.

In another embodiment of the present invention, the drying techniqueemployed to form the above-mentioned consolidated polymer structures canbe freeze drying. The freeze drying technique suitable for use in thepresent invention can be any freeze drying process known in the artsuitable to cause at least a portion of the continuous phase of thelatex to sublimate, thereby creating one or more of the above-describedconsolidated polymer structures. For example, a freeze drying processsuitable for use in the present invention can comprise the steps offreezing the latex followed by applying vacuum to the frozen latex.

After the one or more consolidated polymer structures has been formedvia a drying step, such as those described above, the one or moreconsolidated polymer structures can be reduced in size. The sizereduction process can comprise one or more course and/or fine sizereduction steps, as will be discussed in greater detail below.

In another embodiment of the present invention, consolidation of theemulsion polymer from the latex can be accomplished by freezing thelatex. Formation of the one or more consolidated polymer structures viafreezing can be accomplished by reducing the temperature of the latex tobelow the freezing point of the continuous phase. Depending on thefreeze/thaw stability of the latex, the freezing process may only needto be performed once, or it can be repeated until the desired one ormore consolidated polymer structures are obtained. As used herein, theterm “freeze/thaw stability” denotes the degree to which the polymerportion of a latex can resist coagulation or flocculation when frozen asdetermined by ASTM method D2243. Thus, a latex having a higherfreeze/thaw stability can undergo multiple freeze/thaw cycles in orderto obtain one or more consolidated polymer structures. In oneembodiment, the latex of the present invention can have a freeze/thawstability of less than 5 cycles, less than 3 cycles, or less than 1cycle.

Freezing of the latex may be accomplished by any method known in the artfor lowering the temperature of the latex to the desired degree. Oneexemplary method suitable for use in the present invention involvesplacing the latex into one or more polymeric enclosures, such as, forexample, plastic bags or bottles. Suitable plastics for forming theenclosures include, but are not limited to, high-density polyethylene,nylon, polytetrafluoroethylene, polystyrene, and polyolefins. Theenclosure can then be sealed to prevent loss of the latex and immersedin a coolant bath. The coolant employed in the coolant bath can be anycoolant capable of lowering the temperature of the latex to below thefreezing point of the continuous phase. A suitable coolant for use inthe present invention includes, but is not limited to, liquid nitrogen.

Another exemplary method for freezing the latex of the present inventioninvolves placing the latex into molds of a desired size and thenlowering the temperature of the latex to the desired degree. Similarly,another method includes forming the latex into droplets, followed byfreezing of the droplets. These methods can facilitate later sizereduction of the one or more consolidated polymer structures, discussedbelow.

According to another embodiment of the present invention, consolidationof the emulsion polymer in the latex to form the above-mentioned one ormore consolidated polymer structures can be accomplished by combiningthe latex with salt water. This method can be accomplished by adding thelatex to salt water over a period of time. Conversely, the salt watercan be added to the latex over a period of time. The combination of thelatex and the salt water can be accomplished by any known method in theart. For example, the combination can be accomplished by pump, gravityfeed, or any other suitable method. The latex/salt water mixture can becontinuously stirred during addition.

The salt water suitable for use in the present invention can compriseany ionized compound in water. Though not wishing to be bound by theory,it is believed that ionized species cause agglomeration of the latexpolymer by interfering with the electrical double layer that stabilizesthe latex particles. Examples of ionizable compounds suitable for use inthe present invention include, but are not limited to, alkali metal,alkaline earth metal, and/or transition metal salts of halides,nitrates, phosphates, sulfates, and/or other anions.

In one embodiment, the volume ratio of latex-to-salt water can be in therange of from about 1:2 to about 1:100, in the range of from about 1:5to about 1:50, or in the range of from 1:10 to 1:25. Additionally, theconcentration of salt in the salt water can be at least about 0.5 weightpercent, or at least 5 weight percent. The temperature of the salt waterand latex during mixing can be in the range of from about the freezingpoint of the latex to about 100° C.

Once the desired one or more consolidated polymer structures haveformed, the consolidated polymer structures can be substantiallyisolated by any methods known in the art for accomplishing solid/liquidseparation. The selected isolation technique can be sufficient to removeat least about 70, at least about 90, or at least 95 weight percent ofthe remaining continuous phase. For example, the consolidated polymerstructures can be substantially isolated via decantation, filtration,screening, and/or centrifugation. After the one or more consolidatedpolymer structures have been substantially isolated, they can undergosize reduction as discussed in further detail below.

According to another embodiment of the present invention, consolidationof the emulsion polymer in the latex to form the above-mentioned one ormore consolidated polymer structures can be accomplished by combiningthe latex with a water-miscible solvent. This method can be accomplishedby adding the latex to the water-miscible solvent over a period of time.Conversely, the water-miscible solvent can be added to the latex over aperiod of time. The combination of the latex and the water-misciblesolvent can be accomplished by any known method in the art. For example,the combination can be accomplished by pump, gravity feed, or any othersuitable method. The resulting mixture can be continuously stirredduring addition.

The water-miscible solvent suitable for use in the present invention cancomprise any water-miscible solvent that is a non-solvent for thepolymer particles when mixed with water. In one embodiment, thewater-miscible solvent can be a non-solvent for the polymer particleseven when not mixed with water. Examples of water-miscible solventssuitable for use in the present invention include, but are not limitedto, C₁ to C₄ alcohols, dimethyl formamide, dimethyl acetamide,tetrahydrofuran, sulfolane, nitromethane, furfural, and/or1-methyl-2-pyrrolidinone.

In one embodiment, the volume ratio of latex-to-water-miscible solventcan be in the range of from about 1:2 to about 1:100, in the range offrom about 1:5 to about 1:50, or in the range of from 1:10 to 1:25. Thetemperature of the water-miscible solvent and latex during mixing can bein the range of from about the freezing point of the latex to about theboiling point of the latex or the boiling point of the water-misciblesolvent, whichever is lower.

Once the desired one or more consolidated polymer structures haveformed, the consolidated polymer structures can be substantiallyisolated by any methods known in the art for accomplishing solid/liquidseparation. The selected isolation technique can be sufficient to removeat least about 70 weight percent, at least about 90 weight percent, orat least 95 weight percent of the remaining continuous phase. Forexample, the consolidated polymer structures can be substantiallyisolated via decantation, filtration, screening, and/or centrifugation.After the one or more consolidated polymer structures have beensubstantially isolated, they can undergo size reduction as discussed infurther detail below.

In another embodiment of the invention, consolidation of the emulsionpolymer from the latex to form the above-mentioned one or moreconsolidated polymer structures can be accomplished by adissolution/precipitation technique. In this embodiment, the polymerparticles can be dissolved by combining the latex with a solvent for thepolymer. After the polymer has been at least partially dissolved, thepolymer can be precipitated to form the one or more consolidated polymerstructures. In one embodiment, at least about 70 weight percent, atleast about 90 weight percent, or at least 95 weight percent of thepolymer can be dissolved in the solvent prior to precipitation. Anydissolution/precipitation techniques known in the art can be employed inthe present invention.

In one embodiment, the solvent for use in the dissolution/precipitationtechnique can be a low-volatility solvent. Examples of low volatilitysolvents suitable for use in the present invention include, but are notlimited to, tetrahydrofuran and/or toluene. The concentration of latexin the solvent can be less than about 20 weight percent, less than about15 weight percent, or less than 10 weight percent based on the combinedweight of the latex and solvent.

After the polymer has been at least partially dissolved, any methodknown in the art for precipitating a solute out of solution can beemployed. Suitable precipitation techniques include, but are not limitedto, contacting the solution with an alcohol or other non-solvent, or byflashing the solution to remove at least a portion of the volatilecomponents of the solution. As used herein, the term “flashing” denotesa process whereby at least a portion of a solution is vaporized bysudden decrease in pressure and/or increase in temperature.

Once the desired one or more consolidated polymer structures have formed(i.e., precipitated), the consolidated polymer structures can besubstantially isolated by any methods known in the art for accomplishingsolid/liquid separation, provided any solvent and/or continuous phaseremains after precipitation. The selected isolation technique can besufficient to remove at least about 70 weight percent, at least about 90weight percent, or at least 95 weight percent of the remainingcontinuous phase and/or solvent. For example, the consolidated polymerstructures can be substantially isolated via decantation, filtration,screening, and/or centrifugation. After the one or more consolidatedpolymer structures have been substantially isolated, they can undergosize reduction as discussed in further detail below.

Regardless of which of the above-described methods is employed informing the one or more consolidated polymer structures, in oneembodiment of the present invention, the size of the one or moreconsolidated polymer structures can be decreased to thereby formmodified polymer particles. Any method known in the art for reducing theparticle size of a polymer-containing material can be employed in thepresent invention. In one embodiment, as described in greater detailbelow, the one or more consolidated polymer structures can undergo amulti-stage particle size reduction, including coarse size reductionfollowed by fine size reduction to form the modified polymer particles.

In some of the embodiments described above for forming the one or moreconsolidated polymer structures, the procedure employed may result inconsolidated polymer structures having relatively large diameters (e.g.,greater than 0.75 inches). Accordingly, the one or more consolidatedpolymer structures can optionally undergo coarse size reduction to formintermediate polymer particles. In one embodiment, the one or moreconsolidated polymer structures can undergo coarse size reductionsufficient to achieve intermediate polymer particles having an averagesize of less than about 2.5 inches on each side, less than about 1.5inches on each side, or less than 0.75 inches on each side. Coarse sizereduction of the one or more consolidated polymer structures can beachieved by any methods known in the art. Examples of methods suitablefor use for coarse size reduction in the present invention include, butare not limited to, pulverizing via impact hammers, grinders and/orchoppers. Additionally, the temperature of the one or more consolidatedpolymer structures can be maintained below the glass transitiontemperature of the polymer during coarse size reduction.

In one embodiment, at least a portion of the one or more consolidatedpolymer structures (or, optionally, at least a portion of theintermediate polymer particles) can be reduced to a finely divided state(i.e., modified polymer particles). As used herein, the term “finelydivided state” when used to describe a particulate material shall denotean average particle size of less than 2,000 μm. Any technique known inthe art for reducing the particle size of a polymer can be employed inthe present invention. In one embodiment, at least a portion of the oneor more consolidated polymer structures can be subject to cryogrinding.As used herein, the term “cryogrinding” shall denote any process wherebya polymer is reduced to a finely divided state at cryogenictemperatures. As used herein, the term “cryogenic temperature” shalldenote any temperature below the glass transition temperature of thepolymer being ground.

The temperature of the one or more consolidated polymer structures (or,optionally, the intermediate polymer particles) can be lowered tocryogenic temperatures prior to being reduced to a finely divided state.In one embodiment, the reduction in temperature of the consolidatedpolymer structures can be obtained by contacting the consolidatedpolymer structures with liquid nitrogen. The resulting low-temperatureconsolidated polymer structures can then be introduced into a cold milland ground to achieve the desired particle size.

Optionally, a partitioning agent can be added to the consolidatedpolymer structures during grinding to help prevent the freshly exposedsurfaces of the polymer from sticking together. Examples of suitablepartitioning agents useful in the present invention include, but are notlimited to, alumina, silica, calcined clay, talc, carbon black, calciumstearate, and/or magnesium stearate. The amount of partitioning agentemployed in the grinding process can be less than about 35 weightpercent, less than about 30 weight percent, or less than 25 weightpercent based on the total weight of the consolidated polymer structuresand partitioning agent.

As discussed above, the one or more consolidated polymer structures canbe formed via freezing. In one embodiment of the present invention, theconsolidated polymer structures formed via this method can undergo sizereduction while still frozen in the continuous phase. Furthermore, asmentioned above the latex can be frozen in a packaging material. Thispackaging material can optionally undergo size reduction concurrentlywith the consolidated polymer structures and frozen continuous phase.

The frozen latex, including the continuous phase and optionally thepackaging material, can first be pulverized into intermediate polymerparticles, as described above (e.g., chunks having an average size ofless than 2.5 inches on each side). If the latex is freeze-thaw stableas defined above, coarse reduction can occur below the freezing point ofthe continuous phase of the latex. If the latex is not freeze-thawstable, coarse reduction can occur at any reasonable temperature thatdoes not impact product quality.

After coarse grinding, the intermediate polymer particles can be reducedto a finely divided state, employing methods such as those describedabove, in order to produce modified polymer particles. In oneembodiment, fine size reduction can be performed at a temperature belowthe glass transition temperatures of both the polymer and the packagematerial, if present, and at a temperature below the freezing point ofthe continuous phase of the latex.

In an alterative embodiment of the present invention, theabove-described one or more consolidated polymer structures can beformed and reduced in size in a concurrent process. In this embodiment,the above-described latex containing emulsion polymer particles can befed into a mill concurrently with a gas stream having a temperatureabove that of the latex (e.g., hot air). The temperature and velocity ofthe gas stream can be adjusted to obtain the desired residual moisturecontent in the resulting modified polymer particles. In one embodiment,at least about 70 weight percent, at least about 90 weight percent, orat least 95 weight percent of the continuous phase can be removed duringthe concurrent formation/reduction process.

Regardless of which of the above-described methods is employed, theresulting modified polymer particles can have a mean particle size inthe range of from about 5 to about 800 micrometers, in the range of fromabout 10 to about 600 micrometers, or in the range of from 20 to 400micrometers. Additionally, the modified polymer particles can have aparticle size distribution where D₁₀ denotes the particle size for which10 percent of the total sample volume is smaller and 90 percent islarger, D₅₀ denotes the particle size for which one-half of the samplevolume is larger and one-half is smaller (i.e., median particle size),and D₉₀ is the particle size for which 90 percent of the total samplevolume is smaller and 10 percent is larger. The modified polymerparticles can have a D₁₀ particle size in the range of from about 0.5 toabout 15 μm, in the range of from about 1 to about 12 μm, or in therange of from 2 to 10 μm. The modified polymer particles can have a D₅₀particle size in the range of from about 10 to about 90 μm, in the rangeof from about 20 to about 80 μm, or in the range of from 30 to 70 μm.Additionally, the modified polymer particles can have a D₉₀ particlesize in the range of from about 80 to about 170 μm, in the range of fromabout 90 to about 160 μm, or in the range of from 100 to 150 μm. As willbe discussed in greater detail below, the resulting modified polymerparticles can be dispersed in a carrier fluid for use as a drag reducer.In one embodiment, the resulting drag reducer can comprise modifiedpolymer particles in the form of a suspension in a carrier fluid.

In one embodiment of the present invention, the modified polymerparticles can be combined with a carrier fluid in order to form a dragreducer. As used herein, the term “drag reducer” shall denote acomposition that when added to a fluid flowing through a conduit, iseffective to reduce pressure loss associated with turbulent flow of thefluid through the conduit. The carrier fluid useful in the presentinvention can be any liquid that is a non-solvent for the modifiedpolymer particles. For example, the carrier fluid can comprise waterand/or lower carbon alcohols (e.g., methanol and/or ethanol). In oneembodiment, the modified polymer particles and the carrier fluid can beadded to a mixing tank and mixed in order to form a drag reducer. Theamount of modified polymer particles added to the carrier fluid can besufficient to form a drag reducer having at least about 5 weight percentpolymer, in the range of from about 10 to about 40 weight percentpolymer, or in the range of from 15 to 35 weight percent polymer. In oneembodiment, the carrier fluid can comprise other components to aid inthe formation and/or maintenance of the drag reducer. These componentscan be added to the carrier fluid before, during, and/or after themodified particles are mixed with the carrier fluid. Such componentsinclude, but are not limited to, density balancing agents, freezeprotection agents, suspension stabilizers, wetting agents, anti-foamingagents, and/or thickening agents.

Density balancing agents/freeze protection agents useful in the presentinvention include, but are not limited to, ethylene glycol and propyleneglycol. The amount of density balancing agent/freeze protection agentemployed in the present invention can be in the range of from about 10to about 60 weight percent based on the weight of the carrier fluid.

Suspension stabilizers useful in the present invention include, but arenot limited to talc, tri-calcium phosphate, magnesium stearate, silica,polyanhydride polymers, sterically hindered alkyl phenol antioxidants,and graphite. The amount of suspension stabilizer employed can beminimized or eliminated where possible to reduce the amount of materialin the drag reducer that does not act as a drag-reducing agent. Theamount of the suspension stabilizer added can be in the range of fromabout 0 to about 40 weight percent, in the range of from about 5 toabout 25 weight percent, or in the range of from 8 to 12 weight percentbased on the weight of the carrier fluid.

A wetting agent, such as a surfactant may be added to aid in thedispersal of the modified polymer particles. Non-ionic surfactantssuitable for use as a wetting agent in the present invention include,but are not limited to, linear secondary alcohol ethoxylates, linearalcohol ethoxylates, and/or alkylphenol exthoxylates. Anionicsurfactants suitable for use as a wetting agent in the present inventioninclude, but are not limited to, alkyl benzene sulfonates and/or alcoholethoxylate sulfates (e.g., sodium lauryl sulfate). The amount of wettingagent added can be in the range of from about 0.01 to about 1 weightpercent, or in the range of from 0.01 to 0.1 weight percent, based onthe weight of the carrier fluid.

In order to prevent foaming of the carrier fluid/modified polymerparticle mixture during agitation, a suitable anti-foaming agent can beused. Examples of anti-foaming agents suitable for use in the presentinvention include, but are not limited to, ANTIFOAM products (availablefrom Dow Corning, Midland, Mich.), and BUBBLE BREAKER products(available from Witco Chemical Company, Organics Division). The amountof anti-foaming agent employed can be less than about 1 weight percent,based on the weight of the carrier fluid.

After the carrier fluid/modified polymer particle mixture is formed, athickening agent can be added to increase the viscosity of the mixture.Typical thickening agents are high molecular weight, water-solublepolymers. Thickening agents useful in the present invention include, butare not limited to, polysaccharides, xanthum gum, carboxymethylcellulose, hydroxypropyl guar, and/or hydroxyethyl cellulose.

In another embodiment of the invention, the modified polymer particlescan be added to the continuous phase of a latex already containingemulsion polymerized polymer particles in order to form a drag reducer.The latex of this embodiment can be prepared as described above. Themodified polymer particles can be added to the latex in an amountsufficient to produce a drag reducer containing up to about 25 weightpercent modified polymer particles based on the entire weight of thedrag reducer. Additionally, the resulting drag reducer can compriseun-modified emulsion polymer particles (i.e., initial emulsion polymerparticles) in the range of from about 10 to about 60 percent by weightof the drag reducer, or in the range of from 40 to 50 percent by weightof the drag reducer.

In one embodiment of the present invention, the above-described dragreducers can be added to a hydrocarbon-containing fluid. The resultingtreated hydrocarbon-containing fluid can then be transported through apipeline. The hydrocarbon-containing fluid can comprise a liquid phasehydrocarbon, a non-liquid phase hydrocarbon, and/or a non-hydrocarbonfluid. In one embodiment, the hydrocarbon-containing fluid can compriseat least about 50 weight percent of a liquid phase hydrocarbon.Additionally, the hydrocarbon-containing fluid can comprise crude oil.

The resulting treated hydrocarbon-containing fluid can comprise acumulative amount of the drag reducing polymers sufficient to achieve areduction in drag associated with the turbulent flow of thehydrocarbon-containing fluid through the pipeline of at least about 5percent, at least about 10 percent, or at least 15 percent. In oneembodiment, the treated hydrocarbon-containing fluid can have acumulative concentration of drag reducing polymers in the range of fromabout 0.1 to about 500 parts per million by weight (“ppmw”), in therange of from about 0.5 to about 200 ppmw, in the range of from about 1to about 100 ppmw, or in the range of from 2 to 50 ppmw. In oneembodiment, at least about 50 weight percent, at least about 75 weightpercent, or at least 95 weight percent of the polymer particles from thedrag reducer can be dissolved by the hydrocarbon-containing fluid.

The following examples are intended to be illustrative of the presentinvention in order to teach one of ordinary skill in the art to make anduse the invention and are not intended to limit the scope of theinvention in any way.

EXAMPLES Example 1 Preparation of Drag Reducer Polymers

Two batches (Batch 1 and Batch 2) of drag reducing polymers wereprepared by emulsion polymerization employing the following procedure.Polymerization was performed in a 185-gallon stainless steel, jacketedreactor with a mechanical stirrer, thermocouple, feed ports, andnitrogen inlets/outlets. The reactor was charged with 440 lbs of monomer(2-ethylhexyl methacrylate), 565.3 lbs of de-ionized water, 68.3 lbs ofPolystep B-5 (surfactant, available from Stepan Company of Northfield,Ill.), 1.24 lbs of potassium phosphate monobasic (pH buffer), 0.97 lbsof potassium phosphate dibasic (pH buffer), and 33.2 grams of ammoniumpersulfate, (NH₄)₂S₂O₈ (oxidizer).

The monomer and water mixture was agitated at 110 rpm while being purgedwith nitrogen to remove any traces of oxygen in the reactor and wascooled to about 41° F. The two surfactants were added and the agitationwas slowed down to 80 rpm for the remainder of the batch. The buffersand the oxidizer were then added. The polymerization reaction wasinitiated by adding into the reactor 4.02 grams of ammonium iron(II)sulfate, Fe(NH₄)₂(SO₄)₂·6H₂O in a solution of 0.010 M sulfuric acidsolution in DI water at a concentration of 1,117 ppm at a rate of 5g/min. The solution was injected for 10 hours to complete thepolymerization. The resulting latex was pressured out of the reactorthrough a 5-micron bag filter and stored.

The resulting drag reducer was a latex containing poly(2-ethylhexylmethacrylate) as the active ingredient. The sample had a solids contentof 41.2 percent by mass and a nominal polymer content of 40 percent. Thedensity of the sample was 1.0005 g/mL. The continuous phase was 100%water.

Example 2 Polymer Consolidation and Reduction

The latexes of Batch 1 and Batch 2, as prepared in Example 1, eachunderwent the following procedure for increasing the particle size oftheir respective polymer particles. The polymer particles of the latexwere agglomerated using a thin-layer drying technique. For thisprocedure, the latex was spread in a thin layer on sheet pans. Employinga fan, room temperature air was blown across the pans overnight toevaporate the continuous phase from the latex. After drying, theresulting agglomerated polymer was manually broken apart with a metalhammer into pieces of agglomerated polymer of suitable size to becryoground.

After the agglomerated polymers were manually reduced in size, eachbatch was subjected to cryogrinding in a hammermill using the followingprocedure. 850 grams of each batch were combined with 365 grams ofcalcium stearate partitioning agent in separate plastic containers andshaken to mix. The containers and their contents were pre-chilled byplacing them in dry-ice prior to cryogrinding. Each mixture was thenindividually placed into dewar flasks and frozen with liquid nitrogen.The mixtures were then separately ground by slowly feeding each mixtureto a hammermill over a period of approximately 10 minutes. Duringgrinding, the temperature of the hammermill was kept below the glasstransition temperature of the polymer using liquid nitrogen. Theresulting two batches of cryoground drag reducing polymers (i.e.,modified polymer particles) were then divided into three sub-batcheseach: 1A, 1B, 1C; and 2A, 2B, 2C.

Example 3 Suspension Preparation

Each of the 6 sub-batches prepared in Example 2 was separately suspendedin an aqueous carrier fluid according to the following procedure. Thecryoground polymer was first sieved in order to eliminate undesiredlumps. Next, 434.98 g of de-ionized water, 11.48 g of TERGITOL 15-S-7(surfactant, available from Dow Corning Corp., Midland, Mich.), and 3.82g of ANTIFOAM 1410 (available from Dow Corning Corp., Midland, Mich.)were mixed into a 1 L plastic container. The mixture was then stirred at600 rpm for 2 minutes. 230.02 g of the cryoground polymer was addedslowly over a period of approximately 3 to 4 minutes while continuallystirring the mixture at 600 rpm. Once all of the cryoground polymer wasadded, the mixture was stirred at 600 rpm for an additional 10 minutes.Next, 19.74 g of AQU D-3334 HEC (hydroxyethylcellulose, manufactured byAqualon Company) was injected into the suspension using a 50 mL syringe.The suspension was then stirred at a speed of 1200 rpm for 10 minutes.

Example 4 Particle Size Analyses

The particle sizes of the cryoground polymer in the suspensions preparedin Example 3 were analyzed employing a BECKMAN COULTER LS Particle SizeAnalyzer, model LS 230, Small Volume Module. Table 1 below displays theresults from the analyses, including the mean particle size.Additionally, particle size distributions are given for each sub-batch,where D₁₀ denotes the particle size for which 10 percent of the totalsample volume is smaller and 90 percent is larger, D₅₀ denotes theparticle size for which one-half of the sample volume is larger andone-half is smaller (i.e., median particle size), and D₉₀ is theparticle size for which 90 percent of the total sample volume is smallerand 10 percent is larger.

TABLE 1 Results of Particle Size Analyses Mean Particle Sub-Batch Size(μm) D₁₀ (μm) D₅₀ (μm) D₉₀ (μm) 1A 72.31 8.03 58.97 140.80 1B 70.74 6.2354.18 142.80 1C 68.84 7.23 55.44 137.80 2A 68.04 8.26 56.01 141.50 2B53.41 4.87 42.30 112.10 2C 50.88 4.58 40.68 110.10

Typically, emulsion polymers in latex form will have a mean particlesize of less than about 1 micrometer. As can be seen by looking at theresults in Table 1, the mean particle size of each of the emulsionpolymers after consolidation and size reduction performed in Example 2is greater than the mean particle size of typical emulsion polymers inlatex form.

Numerical Ranges

The present description uses numerical ranges to quantify certainparameters relating to the invention. It should be understood that whennumerical ranges are provided, such ranges are to be construed asproviding literal support for claim limitations that only recite thelower value of the range as well as claims limitation that only recitethe upper value of the range. For example, a disclosed numerical rangeof 10 to 100 provides literal support for a claim reciting “greater than10” (with no upper bounds) and a claim reciting “less than 100” (with nolower bounds).

Definitions

As used herein, the terms “a,” “an,” “the,” and “said” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the term “consolidated polymer structure” refers topolymer particles or structures having an increased average particlesize compared to the average particle size of the polymer particlesprior to consolidation.

As used herein, the terms “containing,” “contains,” and “contain” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

As used herein, the term “cryogrinding” shall denote any process wherebya polymer is reduced to a finely divided state at cryogenictemperatures.

As used herein, the term “cryogenic temperature” shall denote anytemperature below the glass transition temperature of a particularpolymer.

As used herein, the term “drag reducer” refers to a composition that,when added to a fluid flowing through a conduit, is effective to reducepressure loss associated with turbulent flow of the fluid through theconduit.

As used herein, the term “emulsion polymer” shall denote any polymerprepared via emulsion polymerization.

As used herein, the term “finely divided state” when used to describe aparticulate material shall denote an average particle size of less than2,000 μm.

As used herein, the term “flashing” denotes a process whereby at least aportion of a solution is vaporized by sudden decrease in pressure and/orincrease in temperature.

As used herein, the term “freeze/thaw stability” denotes the degree towhich the polymer portion of a latex can resist coagulation orflocculation when frozen as determined by ASTM method D2243.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise” providedabove.

As used herein, the term “HLB number” refers to the hydrophile-lipophilebalance of an amphiphilic compound as determined by the methodsdescribed by W. C. Griffin in J. Soc. Cosmet. Chem., 1, 311 (1949) andJ. Soc. Cosmet. Chem., 5, 249 (1954).

As used herein, the term “high HLB” shall denote an HLB number of 7 ormore.

As used herein, the terms “including,” “includes,” and “include” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

As used herein, the term “polymer” refers to homopolymers, copolymers,terpolymers of one or more chemical species.

As used herein, the term “turbulent flow” refers to fluid flow having aReynolds number of at least 2,000.

As used herein, the term “weight average molecular weight” refers to themolecular weight of a polymer calculated according to the followingformula: Σ_(i)(N_(i)M_(i) ²)/Σ_(i)(N_(i)M_(i)), where N_(i) is thenumber of molecules of molecular weight M_(i).

Claims Not Limited to The Disclosed Embodiments

The preferred forms of the invention described above are to be used asillustration only, and should not be used in a limiting sense tointerpret the scope of the present invention. Modifications to theexemplary embodiments, set forth above, could be readily made by thoseskilled in the art without departing from the spirit of the presentinvention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

1.-24. (canceled)
 25. A drag reducer, comprising: a plurality of first non-polyalphaolefin latex polymer particles, wherein the plurality of first non-polyalphaolefin latex polymer particles have a weight average molecular weight of at least about 1×10⁶ g/mol and an average particle size ranging from about 5 micrometers to about 800 micrometers; and a plurality of second non-polyalphaolefin latex polymer particles having an average particle size of less than about 1 micrometer.
 26. The drag reducer of claim 25, wherein the average particle size of the plurality of first non-polyalphaolefin latex polymer particles ranges from about 10 micrometers to about 600 micrometers.
 27. The drag reducer of claim 25, wherein the plurality of first non-polyalphaolefin latex polymer particles is dispersed in a carrier fluid.
 28. The drag reducer of claim 27, wherein the carrier fluid comprises water, alcohol, or a combination thereof.
 29. The drag reducer of claim 25, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of C4-C20 alkyl, C6-C20 substituted or unsubstituted aryl, or aryl-substituted C1-C10 alkyl ester derivatives of methacrylic acid or acrylic acid.
 30. The drag reducer of claim 25, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of 2-ethylhexyl methacrylate monomers.
 31. The drag reducer of claim 25, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of 2-ethylhexyl methacrylate monomers and residues of butyl acrylate monomers.
 32. The drag reducer of claim 31, wherein the plurality of first non-polyalphaolefin latex polymer particles is dispersed in a carrier fluid, and the carrier fluid comprises water, alcohol, or a combination thereof.
 33. A drag reducer, comprising: a plurality of first non-polyalphaolefin latex polymer particles, wherein the plurality of first non-polyalphaolefin latex polymer particles have a weight average molecular weight of at least about 1×10⁶ g/mol and an average particle size ranging from about 20 micrometers to about 400 micrometers; and a plurality of second non-polyalphaolefin latex polymer particles having an average particle size ranging from about 10 nm to about 500 nm.
 34. The drag reducer of claim 33, wherein the plurality of first non-polyalphaolefin latex polymer particles is dispersed in a carrier fluid.
 35. The drag reducer of claim 34, wherein the carrier fluid comprises water, alcohol, or a combination thereof.
 36. The drag reducer of claim 33, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of C4-C20 alkyl, C6-C20 substituted or unsubstituted aryl, or aryl-substituted C1-C10 alkyl ester derivatives of methacrylic acid or acrylic acid.
 37. The drag reducer of claim 33, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of 2-ethylhexyl methacrylate monomers.
 38. The drag reducer of claim 33, wherein the plurality of first non-polyalphaolefin latex polymer particles comprises repeating units of residues of 2-ethylhexyl methacrylate monomers and residues of butyl acrylate monomers.
 39. A process for forming a drag reducer, comprising: forming a first plurality of polymer particles, wherein the first plurality of particles have a first average particle size of less than about 1 micrometer; consolidating at least a portion of the first plurality of polymer particles to form a second plurality of polymer particles, wherein the second plurality of polymer particles have a second average particle size greater than the first average particle size; and forming a third plurality of polymer particles from the second plurality of polymer particles, wherein the third plurality of polymer particles have a third average particle size less than the second average particle size and greater than the first average particle size.
 40. The process of claim 39, wherein the first average particle size ranges from about 10 nm to about 500 nm.
 41. The process of claim 39, wherein the second average particle size is greater than 0.75 inches.
 42. The process of claim 39, wherein the third average particle size ranges from about 5 micrometers to about 800 micrometers.
 43. The process of claim 42, wherein the third average particle size ranges from about 20 micrometers to about 400 micrometers.
 44. The process of claim 39, wherein the first plurality of polymer particles is formed by emulsion polymerization.
 45. The process of claim 39, wherein the consolidating at least portion of the first plurality of particles comprises adding a water-miscible solvent to the first plurality of polymer particles. 